Urea composition and method for producing same

Abstract

Disclosed is a particulate, urea-containing composition, to a method and apparatus for producing it, to the use thereof as fertilizer, as technical urea or as feed additive, and to the use of an additive for producing a particulate, urea-containing composition.

The invention claimed is: 
     
       1. A particulate composition comprising
 (i) urea; 
 and an additive comprising component (ii) and at least one of components (iii) and (iv): 
 (ii) a combination of polyethylenimine and polyvinyl alcohol or a combination of polyethylenimine and polyvinylamine; 
 (iii) at least one aliphatic C 2 -C 8  dialdehyde; and 
 (iv) at least one compound selected from the group of aliphatic dixcarboxylic acids, their salts and anhydrides, aliphatic tricarboxylic acids, their salts and anhydrides, aromatic dicarboxylic acids, their salts and anhydrides, and aldehydic acids, their salts and anhydrides; 
 where the weight fraction of component (i) is >60 wt % and the weight fraction of the sum of components (ii) and (iii) in the composition is <1 wt %. 
 
     
     
       2. The particulate composition of  claim 1 , comprising
 (i) urea; 
 and an additive comprising component (ii) and one or both of components (iii) and (iv): 
 (ii) a combination of polyethylenimine and polyvinylamine; 
 (iii) ethanedial and/or glutaraldehyde; 
 (iv) at least one compound selected from the group consisting of oxalic acid, succinic acid, citric acid, phthalic acid, phthalic anhydride, glyoxylic acid, and salts thereof, 
 where the weight fraction of component (i) is >97 wt % and the weight fraction of the sum of components (ii), (iii), and (iv) in the composition is <1 wt %. 
 
     
     
       3. The particulate composition of  claim 2 , wherein the polyethylenimine of component (ii) has a molecular weight in the range of 500-2 000 000 Da. 
     
     
       4. The particulate composition of  claim 3 , wherein the polyvinylamine of component (ii) has a molecular weight in the range of 500-1 000 000 Da. 
     
     
       5. The particulate composition of  claim 1 , wherein the weight fraction of component (i) in the composition is >98 wt %. 
     
     
       6. The particulate composition of  claim 1 , wherein the weight fraction of the sum of components (ii), (iii), and (iv) in the composition is <0.5 wt %. 
     
     
       7. The particular composition of  claim 1 , wherein the weight fraction of component (i) is more than 97 wt % and the weight fraction of the sum of components (ii), (iii), and (iv) in the composition is less than 1 wt %. 
     
     
       8. A method for producing a particulate composition comprising urea, comprising the steps of:
 (A) providing a urea-containing solution; and 
 (B) granulating the urea-containing solution with addition of an additive defined as defined in  claim 1 . 
 
     
     
       9. The method of  claim 8 , wherein the urea content of the solution is >60 wt %. 
     
     
       10. The method of  claim 8 , wherein the granulation in step (B) takes place by means of fluidized bed granulation, comprising the steps of:
 (B1) providing urea-containing seeds; 
 (B2) fluidizing the urea-containing seeds; 
 (B3) spraying the urea-containing solution onto the seeds, using an additive as defined in  claim 1 . 
 
     
     
       11. The method of  claim 8 , wherein the temperature of the urea-containing solution is >130° C. 
     
     
       12. The method of  claim 8 , further comprising step (C):
 (C) separating the particulate urea composition after its production into three fractions is separated, where:
 one fraction (F1) contains particles having the desired target size, 
 one fraction (F2) contains particles having a size above the desired target size, and 
 one fraction (F3) contains particles having a size below the desired target size. 
 
 
     
     
       13. The method of  claim 12 , further comprising step (D):
 (D) wet scrubbing.